The present invention relates generally to booklet manufacturing methods and apparatuses and more particularly to methods and apparatuses for manufacturing booklets from a multiplicity of continuous strips of paper having printed matter thereon.
Booklets of the type relevant here comprise a plurality of inner pages and front and back cover parts. In a conventional booklet manufacturing process, the inner pages of the booklet are formed by adhering together a plurality of continuous paper strips along a longitudinal center line of each and then folding them over, employing conventional adhering and folding operations to provide a continuous paper strip having a folded longitudinal edge or spine and a multiplicity of plies each of which corresponds to a page in the booklets. The multi-ply continuous strip constituting the inner pages of the booklets (hereinafter called the inner strip) is then inserted within and adhered to another continuous paper strip from which are formed the covers for the booklets. This last-described operation is usually accomplished by applying a longitudinal strip of adhesive along the cover strip, with the latter in an unfolded condition, laying the folded, multi-ply inner strip atop the cover strip, with the spine of the inner strip located along or adjacent the strip of adhesive on the cover strip, pressing the two strips together to adhere them, and folding one part of the unfolded strip over the inner strip to form a cover for the booklets.
When the cover strip is folded over, in the manner described in the preceding paragraph, there is formed on the cover strip a longitudinal fold edge adjacent the spine on the inner strip pages. It is desirable that the longitudinal fold edge on the cover be a sharp, neat fold, for aesthetic or appearance purposes. A sharp, neat fold is usually effected by tensioning the strips while they undergo folding. If the fold is not sharp enough or neat enough, this can usually be corrected in conventional methods by increasing the tension on the strips while they undergo folding.
After the cover strip has been folded around the inner strip, booklets are formed from the resulting composite strip by making transverse cuts at regularly spaced locations along the composite strip.
It is sometimes desirable to provide the front cover part of the booklet with a transverse slit. An example of such a booklet is one in which the cover is a ticket holder for holding air line tickets, for example. The front cover part of the ticket holder has a pocket on the inside thereof, and there is a transverse slit on the outside of the front cover part which communicates with the pocket.
In the booklet manufacturing operation, the front and back cover parts of the ticket holders are formed from a continuous cover strip having first and second parts extending in adjacent relationship along a longitudinal folding line, with transverse slits cut at longitudinally spaced intervals on the first part of the strip. Each transverse slit corresponds to one ticket holder.
In lapped, folded relation with the first part of the continuous cover strip is an additional longitudinally extending part having a terminal edge adhered to the first part adjacent the longitudinal folding line. The first part eventually becomes the front cover part, and the additional part eventually becomes the inside wall of a pocket having an outside wall formed by the front cover part.
As previously noted, the booklet pages are formed from a continuous inner strip of paper having multiple plies, and this inner strip has a transverse dimension corresponding substantially to the transverse dimension of the first part on the cover strip. The inner strip is laid atop the first part of the cover strip, and the first part of the cover strip becomes a bottom cover part under the inner strip during the manufacturing operation. At the time the cover strip is folded over the inner strip, both strips are in tension. The second part of the cover strip is folded along the longitudinal folding line, out of the plane of the cover strip, and then over and atop the multi-ply inner strip to provide a top cover part over the inner strip and a longitudinal edge at the folding line.
When the second part of the cover strip is folded out of the plane of the cover strip, there is a substantial decrease in the amount of tension which is being absorbed by the second part. As a result, there is a significant increase in the amount of tension required to be absorbed by the first part of the cover strip. Because the first part of the cover strip has transverse slits therein, it does not have the strength to withstand the tension it would otherwise withstand without the transverse slits, and there is a danger of tearing transversely from the transverse slit to the longitudinal folding line on the cover strip, during the folding operation when the first part is absorbing increased tension.
To avoid such transverse tearing requires a reduction in the tension in the cover strip, and when the tension in the cover strip is reduced to avoid transverse tearing, the fold obtained along the longitudinal folding line will generally not be a sharp, neat fold.